PTFE (Polytetrafluoroethylene) copper-clad plate with high peeling strength and preparation method of PTFE copper-clad plate

Abstract

The invention discloses a preparation method of a PTFE (polytetrafluoroethylene) copper-clad plate with high peeling strength, which comprises the following steps: grafting itaconic acid to the surface of a PTFE prepreg, then covering copper foils on the two surfaces of the PTFE prepreg, and then carrying out high-temperature laminated sintering treatment to obtain the PTFE copper-clad plate. The invention also claims to protect the PTFE copper-clad plate prepared by the method. According to the preparation method of the high-peeling-strength PTFE copper-clad plate, PTFE molecules in the PTFE prepreg are subjected to grafting modification treatment through itaconic acid, so that the characteristic of low surface energy of PTFE is effectively improved, the binding force between the PTFE and the copper foil is greatly enhanced, and the dielectric property of the PTFE copper-clad plate is not damaged; meanwhile, the production process is green, environment-friendly and pollution-free, and the preparation method is short in time consumption, simple to operate and convenient for industrial large-scale production and application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high polymer material and composite material preparation, in particular to a method for modifying PTFE substrate based on high polymer grafting modification technology and preparing high peel strength PTFE copper clad plate, and a PTFE copper clad plate prepared by the method. BACKGROUND

[0002] PTFE (polytetrafluoroethylene) copper clad plate is a copper clad laminate (CCL) with PTFE as substrate, which has good dielectric properties, can ensure the complete and rapid transmission of signals, and based on the high heat resistance and weather resistance of PTFE, it can work stably in outdoor, large temperature difference and other harsh environments, and is widely used in high frequency circuit boards.

[0003] In practice, PTFE copper clad plate faces a problem in the application process. Due to the high bond energy of C-F in PTFE, PTFE has high chemical inertness and low surface energy, which leads to poor adhesion between PTFE and copper foil, resulting in problems such as copper strip bulging, delamination and even peeling off in PCB processing, which hinders the further use of PTFE (such as in the field of 5G communication). Therefore, how to realize the close pressing of PTFE prepreg and copper foil is a very key technology in the preparation process of PTFE-based copper clad plate. For this reason, people have improved based on this technical problem, such as:

[0004] The patent document with publication number CN 112351591A introduces a method for preparing a copper clad plate with high peel strength. The PTFE material is calendered into a sheet by calendering process, and then a modification agent of Na, naphthalene complex is coated on the surface to improve the adhesion between the composite material and the copper foil. Although the adhesion of the copper clad plate obtained by this method is improved, the Na, naphthalene complex is usually dissolved in organic solvent, and the waste liquid treatment cost is high, which also has certain safety risk to human body and environment; secondly, the modification treatment will also cause adverse effects on the dielectric properties and mechanical properties of the copper clad plate;

[0005] The patent document with publication number CN 103421200B discloses a method for improving the adhesion of PTFE by physical method. The PTFE is placed in organic solvent for ultrasonic cleaning, and then the cleaned PTFE is treated by plasma, so as to improve the adhesion between PTFE and other materials. However, the product treated by this technology has the problems of insufficient adhesion strength and fast failure;

[0006] In the above scheme, although the adhesion performance of PTFE is improved to some extent, other problems also exist, such as in the scheme of the document CN 112351591A, the sodium and naphthalene complex is usually dissolved in an organic solvent, the waste liquid treatment cost is high, there is a certain safety risk to the human body and the environment, and the modification treatment will also adversely affect the dielectric performance and mechanical performance of the copper-clad plate; the product treated in the scheme of the document CN103421200B has the defects of quick viscosity invalidation and insufficient viscosity strength.

[0007] Therefore, it is necessary to seek a preparation method of high peel strength PTFE copper-clad plate which can effectively improve the bonding force between PTFE and copper foil, does not damage the dielectric performance of PTFE, and is safe and environmentally friendly. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a preparation method of high peel strength PTFE copper-clad plate, and also to provide a high peel strength PTFE copper-clad plate prepared by the preparation method.

[0009] To achieve the above purpose, the present application adopts the following technical solutions:

[0010] A preparation method of high peel strength PTFE copper-clad plate, comprising the following steps: grafting itaconic acid to the surface of a PTFE prepreg, then covering copper foil on both sides of the PTFE prepreg, and then performing high-temperature lamination sintering treatment, thereby obtaining the high peel strength PTFE copper-clad plate.

[0011] In the present application, a further preferred scheme is that the PTFE prepreg is prepared by the following steps: coating a fluororesin dispersion liquid on a releasable substrate, then performing drying treatment, obtaining a fluororesin layer on the release paper, and separating the fluororesin layer from the substrate, thereby obtaining the PTFE prepreg.

[0012] In the present application, a further preferred scheme is that the fluororesin dispersion liquid comprises the following components: fluororesin emulsion, inorganic filler, and thickening agent, the weight fraction of the inorganic filler is 40%-70% of the total weight fraction of the fluororesin emulsion and the inorganic filler, and the weight fraction of the thickening agent is 0.5%-3% of the total weight fraction of the fluororesin emulsion and the inorganic filler.

[0013] In the present application, a further preferred scheme is that the fluororesin emulsion is a polytetrafluoroethylene resin emulsion, and the particle size of the fluororesin emulsion is 0.1-0.5 μm.

[0014] In the present application, a further preferred scheme is that the viscosity of the fluororesin emulsion is 90-950 mPa·s.

[0015] In the present application, the further preferred scheme is that the step of grafting itaconic acid onto the surface of the PTFE prepreg is specifically: immersing the PTFE prepreg in an itaconic acid solution, and then grafting the itaconic acid onto the surface of the PTFE prepreg by radiation treatment after taking out.

[0016] In the present application, the further preferred scheme is that the mass concentration of the itaconic acid in the itaconic acid solution is 1%-2%; and more preferably, the solvent of the itaconic acid solution is a mixed solution of water and ethanol in a mass ratio of 2:1.

[0017] In the present application, the further preferred scheme is that the time for immersing the PTFE in the itaconic acid solution is 3-8 min; and the radiation treatment adopts electron beam radiation treatment, and the specific electron beam radiation conditions are: the irradiation voltage is 10 keV-100 keV, and the irradiation dose is 5-100 kGy.

[0018] In the present application, the further preferred scheme is that the irradiation voltage is 80 keV, and / or the irradiation dose is 35 kGy.

[0019] In the present application, the further preferred scheme is that before the copper foil is covered on both sides, a plurality of layers of PTFE prepregs are laminated together, and then the copper foil is covered on both sides and high-temperature lamination and sintering treatment are performed.

[0020] In the present application, the further preferred scheme is that the specific conditions of the high-temperature lamination and sintering treatment are: the hot pressing pressure is 50-100 kgf, the hot pressing vacuum degree is-80 kPa to-99 kPa, the hot pressing temperature is 350-400℃, and the holding and pressure maintaining time is 1-6 h.

[0021] The present application also provides a high-peel-strength PTFE copper-clad plate prepared by any of the above preparation methods. Further, the peel strength of the PTFE copper-clad plate is 1.56-3.27 N / mm, and the dielectric constant is 2.192-2.432.

[0022] Compared with the prior art, the present application has the beneficial effects that: by grafting modification of itaconic acid on PTFE, the characteristics of low surface energy of PTFE are effectively improved, the bonding force between PTFE and copper foil is greatly enhanced, the quality defects such as delamination and bulging of the PTFE copper-clad plate in the subsequent processing process can be effectively reduced, and the dielectric properties are not damaged; at the same time, itaconic acid is a bio-based material, which is green, environmentally friendly and pollution-free, and effectively avoids the pollution in the traditional process; in addition, the preparation method of the present application is time-saving, simple to operate, and convenient for industrial large-scale production and application.

[0023] Drawings of the specification

[0024] Figure 1The infrared spectrum of the PTFE prepreg obtained in step (2) of Example 1.

[0025] Figure 2 The infrared spectrum of the PTFE prepreg obtained in step (3) of Example 1. DETAILED DESCRIPTION

[0026] Hereinafter, the present application will be further described in conjunction with specific embodiments, and it should be noted that the following described embodiments or technical features can be combined arbitrarily to form new embodiments, without conflict. Unless otherwise specified, the materials and equipment used in the embodiments can be purchased from the market. The specific embodiments are exemplary and are only used to explain the present application, and cannot be understood as limiting the scope of protection of the present application.

[0027] A preparation method of a high-peel-strength PTFE copper-clad plate (or PTFE-based copper-clad plate), comprising the following steps: grafting itaconic acid onto the surface of a PTFE prepreg, then covering copper foils on both sides of the PTFE prepreg, and then performing high-temperature lamination sintering treatment, to obtain the PTFE copper-clad plate.

[0028] In the present application, grafting itaconic acid onto the surface of the PTFE prepreg means that the C-F bond in the PTFE molecule on the PTFE prepreg is broken to generate free radicals, and then a grafting reaction occurs with the polar monomer itaconic acid, so that the itaconic acid is grafted onto the surface of the PTFE prepreg.

[0029] In the preparation method of the present application, the grafting modification treatment of itaconic acid on PTFE effectively improves the low surface energy characteristics of PTFE, greatly enhances the bonding force between PTFE and copper foil, can effectively reduce the quality defects such as delamination and bulging of the PTFE copper-clad plate in the subsequent processing process, and also does not harm its dielectric properties; at the same time, itaconic acid is a bio-based material, green and environmentally friendly without pollution, effectively avoiding the pollution in the traditional process; in addition, the preparation method of the present application is time-saving, simple to operate, and convenient for industrial large-scale production and application.

[0030] The PTFE prepreg in the present application can be prepared by the following steps: coating a fluororesin dispersion liquid on a releasable substrate, then performing drying treatment, obtaining a fluororesin layer on the release paper, and separating the fluororesin layer from the substrate to obtain the PTFE prepreg.

[0031] The fluororesin dispersion liquid in the application comprises the following components: fluororesin emulsion, inorganic filler, and thickening agent, wherein the weight of the inorganic filler accounts for 40%-70% of the total weight of the fluororesin emulsion and the inorganic filler, and the weight of the thickening agent accounts for 0.5%-3% of the total weight of the fluororesin emulsion and the inorganic filler. If the weight of the inorganic filler is less than 40% of the total weight of the fluororesin emulsion and the inorganic filler, and the weight of the thickening agent is less than 0.5% of the total weight of the fluororesin emulsion and the inorganic filler, the resin film-forming property will be poor. If the weight of the inorganic filler is more than 70% of the total weight of the fluororesin emulsion and the inorganic filler, and the weight of the thickening agent is more than 3% of the total weight of the fluororesin emulsion and the inorganic filler, the surface dielectric property of the product will be affected, and the surface dielectric property of the prepared PTFE prepreg will be reduced.

[0032] The inorganic filler can be any one or a mixture of at least two of the following: silicon dioxide, titanium dioxide, aluminum oxide, aluminum nitride, barium sulfate, boron nitride, and calcium carbonate. Further preferably, the inorganic filler is silicon dioxide and / or titanium dioxide. Compared with other inorganic fillers, titanium dioxide and silicon dioxide are more mature in industrialization and have a lower price. Moreover, the thermal expansion coefficient of titanium dioxide and silicon dioxide is closer to that of copper foil, which can reduce the risk of thermal stress delamination. In addition, silicon dioxide has the advantages of low dielectric constant, low loss, and good dispersibility. Titanium dioxide has good thermal stability and can be better used in the PTFE high-temperature sintering process.

[0033] The thickening agent can be a modified urea solution. The use of a modified urea thickening agent can effectively adjust the viscosity of the PTFE slurry at a small amount of addition, so that the slurry is easy to coat and has good anti-settling performance. Further preferably, the modified urea solution can contain N-methyl pyrrolidone, N-ethyl pyrrolidone, or other solvent components.

[0034] The fluororesin emulsion can be a polytetrafluoroethylene resin emulsion. The particle size of the fluororesin emulsion is 0.1-0.5 μm. Further preferably, the particle size of the fluororesin emulsion is 0.3 μm. The fluororesin emulsion with this particle size has good compatibility with the inorganic filler, which improves the film-forming uniformity and stability of the product.

[0035] The viscosity of the fluororesin dispersion liquid is 90-950 mPa·s. If the viscosity is less than 90 mPa·s, the flowability of the slurry is strong, which increases the coating difficulty and causes the coating film to flow easily when moving, resulting in uneven film thickness. If the viscosity is more than 950 mPa·s, the drying time is increased, and air bubbles are difficult to discharge, which easily forms air hole defects. Further preferably, the viscosity is 150-700 mPa·s, and more preferably, the viscosity is 200-500 mPa·s. The viscosity of the fluororesin dispersion liquid can be adjusted by adjusting the amount of the thickening agent.

[0036] The releaseable substrate in the application can be any one of polyimide substrate, polyetherimide substrate, copper foil and aluminum foil.

[0037] In the application, the step of grafting itaconic acid onto the surface of the PTFE prepreg is specifically as follows: immersing the PTFE prepreg in an itaconic acid solution, and then taking out the PTFE prepreg and grafting itaconic acid onto the surface of the PTFE prepreg by radiation treatment. The radiation source for the radiation treatment can be any one of ultraviolet light (UV), gamma rays (γ rays) and electron beam (EB); preferably, the electron beam (EB) is selected as the radiation source, which can cause chemical bond breakage in a very short time without adding a photoinitiator, thereby improving the grafting efficiency of PTFE, and the electron beam is green and environmentally friendly, and does not cause chemical residues and heavy metal pollution.

[0038] In the application, in order to improve the grafting efficiency of PTFE, the mass concentration of itaconic acid in the itaconic acid solution is preferably 1% to 2%, and the grafting rate with PTFE will be reduced when the mass concentration of itaconic acid is less than 1% (not including the number); when the mass concentration of itaconic acid is higher than 2% (not including the number), itaconic acid will undergo homopolymerization, which will also reduce the grafting rate with PTFE. Furthermore, the solvent of the itaconic acid solution is a mixture of water and ethanol in a mass ratio of 2:1.

[0039] In the application, a further preferred scheme is that the PTFE is immersed in the itaconic acid solution for 3 to 8 minutes; the radiation treatment adopts electron beam radiation treatment, and the specific electron beam radiation conditions are as follows: the irradiation voltage is 10 keV to 100 keV, and the irradiation dose is 5 to 100 kGy. For the selection of the immersion time, if the immersion time is less than 3 minutes, the itaconic acid solution is difficult to fully soak the PTFE, which affects the subsequent grafting treatment; if the immersion time is more than 8 minutes, the preparation time will be prolonged. For the radiation voltage and dose, if the irradiation voltage is less than 10 keV and the irradiation dose is less than 5 kGy, the grafting will be incomplete; if the irradiation voltage is higher than 100 keV and the irradiation dose is higher than 100 kGy, the PTFE will be degraded. Furthermore, the immersion time is preferably 6 minutes; furthermore, the irradiation voltage is preferably 80 keV, and / or the irradiation dose is preferably 35 kGy, which will make the PTFE have good grafting efficiency, and thus the copper-clad plate has higher peel strength. Furthermore, an electron accelerator can be used for electron beam radiation (or "irradiation") treatment.

[0040] In the present application, further preferred scheme is that before carrying out the copper foil covering on both sides, several layers of PTFE prepreg are laminated together, and then the copper foil covering on both sides and high temperature lamination sintering treatment are carried out; the several layers refer to 2 layers and more than 2 layers, preferably 2-5 layers, and further preferably 2 layers. For the number of layers of PTFE prepreg lamination, the number of layers can be adjusted according to the requirements of different sample thickness, and more layers may cause the middle layer of the product to be not fully combined and delaminate, which requires higher pressing temperature and time, and increases the production cost; 2-5 layers are relatively optimal for the overall production efficiency, performance and cost of the product.

[0041] In the present application, the specific conditions of the high temperature lamination sintering treatment are as follows: hot pressing pressure is 50-100 kgf, hot pressing vacuum degree is -80 to -99 kPa (relative pressure, i.e. 80-99 kPa lower than standard atmospheric pressure), hot pressing temperature is 350-400℃, holding and pressure maintaining time is 1-6h; using the above range of high temperature lamination sintering treatment conditions, PTFE can be fully flowed and combined, the existence of bubbles in the sheet layer is reduced, and a PTFE copper clad plate with excellent performance is prepared, and the copper clad plate prepared by using the above parameters has no bubbles on the surface and will not appear the phenomenon of under-pressure delamination. Further preferred scheme is that the hot pressing pressure is preferably 70-90 kgf, the hot pressing vacuum degree is -98 kPa, the hot pressing temperature is 370-390℃, and the holding and pressure maintaining time is 2-4h.

[0042] In the present application, further, the peel strength of the PTFE copper clad plate is 1.56-3.27 N / mm, and the dielectric constant is 2.192-2.342; the peel strength and the dielectric constant in the present application refer to the dielectric constant obtained by testing the PTFE copper clad plate by using the method 2.5.5.2 in the electrical test method of part 2.5 of the standard IPC-TM-650, and the peel strength obtained by testing the PTFE copper clad plate by using the method in part 2.4.8 of the standard IPC-TM-650.

[0043] The specific substances used in the following Examples 1-4 and Comparative Examples 1-2 of the present application are as follows: the fluororesin emulsion is a polytetrafluoroethylene emulsion, which is a PTFE resin emulsion product of Model D210C produced by Daikin Industries, Ltd. of Japan; the inorganic filler is a silica product of Model HB-132 produced by Guangzhou Jibisheng Science and Technology Co., Ltd. and a titanium dioxide product of Model NA-110 produced by Hebei Maisen Titanium Dioxide Co., Ltd.; the thickening agent is a modified urea solution product of Model RHEOBYK-410 produced by BYK-Chemie GmbH; the itaconic acid is from Nanjing Chemical Reagent Co., Ltd., and the solvent in the itaconic acid solution is a mixture of water and ethanol in a mass ratio of 2:1; the sodium-naphthalene complexing agent is a naphthalene sodium treatment liquid product of Model AC-711 produced by Fangzhou (Fokang) Chemical Materials Co., Ltd.; and in the electron beam irradiation, an electron accelerator of Model MEB-160 produced by Jiangsu Zhiren Science and Technology Co., Ltd. is used.

[0044] Example 1

[0045] A preparation method of a high-peel-strength PTFE copper-clad plate, comprising the following steps:

[0046] (1) 100 g of fluororesin emulsion, 83 g of inorganic filler, and 1 g of thickening agent are mixed by high-speed stirring for 1.5 h to obtain a fluororesin dispersion;

[0047] (2) The dispersion obtained in step (1) is coated on a copper foil (a releasable substrate), and then placed in a 350°C oven for baking for 25 min, after which the copper foil is separated from the PTFE prepreg to obtain a PTFE prepreg;

[0048] (3) The PTFE prepreg obtained in step (2) is immersed in an itaconic acid solution (the mass concentration of itaconic acid in the itaconic acid solution is 1.5%) for 6 min, and then taken out and irradiated in an electron accelerator (voltage: 80 keV, dose: 15 kGy) to obtain a PTFE prepreg with high peel strength;

[0049] (4) Two layers of the PTFE prepreg obtained in step (3) are laminated, and the size of the PTFE prepreg is selected to be 380 mm x 280 mm. Copper foils with a thickness of 18 μm are covered on both sides of the laminated prepreg, and high-temperature lamination sintering treatment is performed, with the specific conditions being: hot-pressing pressure: 80 kgf, hot-pressing temperature: 375°C, and holding and pressure-maintaining time: 2.5 h;

[0050] (5) After step (4) is completed, the temperature is lowered to room temperature, and then the pressure is released to obtain a PTFE-based copper-clad plate with high peel strength.

[0051] Example 2

[0052] A preparation method of a high-peel-strength PTFE copper-clad plate, comprising the following steps:

[0053] (1) Take 100 g of fluororesin emulsion, 83 g of inorganic filler, 1 g of thickening agent, and mix them at high speed for 1.5 h; obtain a fluororesin dispersion;

[0054] (2) Apply the dispersion liquid described in step (1) to a copper foil (a releasable substrate), place it in a 350°C oven for 25 minutes, and then separate it from the copper foil to obtain a PTFE prepreg;

[0055] (3) Place the PTFE prepreg obtained in step (2) in a solution of itaconic acid (the mass concentration of itaconic acid in the itaconic acid solution is 1.5%) for 6 minutes, then take it out and place it in an electron accelerator for irradiation (voltage is 80 keV, dose is 25 kGy) to obtain a PTFE prepreg with high peel strength;

[0056] (4) Stack 2 layers of the PTFE prepreg obtained in step (3), and select the size of the PTFE prepreg to be 380 x 280 mm. Cover the two sides of the stacked prepreg with 18 μm thick copper foil and perform high temperature lamination sintering treatment. The specific conditions of the high temperature lamination sintering treatment are: hot pressing pressure is 80 kgf, hot pressing temperature is 375°C, and holding and pressure maintaining time is 2.5 h;

[0057] (5) After step (4) is completed, cool to room temperature and release the pressure to obtain a PTFE-based copper-clad plate with high peel strength.

[0058] Example 3

[0059] A method for preparing a PTFE copper-clad plate with high peel strength, comprising the following steps:

[0060] (1) Take 100 g of fluororesin emulsion, 83 g of inorganic filler, 1 g of thickening agent, and mix them at high speed for 1.5 h; obtain a fluororesin dispersion;

[0061] (2) Apply the dispersion liquid described in step (1) to a copper foil (a releasable substrate), place it in a 350°C oven for 25 minutes, and then separate it from the copper foil to obtain a PTFE prepreg;

[0062] (3) Place the PTFE prepreg obtained in step (2) in a solution of itaconic acid (the mass concentration of itaconic acid in the itaconic acid solution is 1.5%) for 6 minutes, then take it out and place it in an electron accelerator for irradiation (voltage is 80 keV, dose is 25 kGy) to obtain a PTFE prepreg with high peel strength;

[0063] (4) two layers of PTFE prepreg obtained in step (3) are laminated, the size of the PTFE prepreg is selected as 380*280mm, 18μm-thick copper foils are covered on both sides of the laminated prepreg, and high-temperature lamination sintering treatment is performed, the specific conditions of the high-temperature lamination sintering treatment being: hot-pressing pressure 80kgf, hot-pressing temperature 375℃, and holding and pressure-keeping time 2.5h;

[0064] (5) after step (4) is completed, the temperature is lowered to room temperature, and then pressure is released, thereby obtaining a PTFE-based copper-clad plate with high peel strength.

[0065] Example 4

[0066] A method for preparing a PTFE copper-clad plate with high peel strength comprises the following steps:

[0067] (1) 100g of fluororesin emulsion, 83g of inorganic filler, and 1g of thickening agent are mixed by high-speed stirring for 1.5h, thereby obtaining a fluororesin dispersion;

[0068] (2) the dispersion obtained in step (1) is coated on a copper foil (a releasable substrate), and then placed in a 350℃ oven for baking for 25min, after which the copper foil is separated from the PTFE prepreg;

[0069] (3) the PTFE prepreg obtained in step (2) is immersed in a solution of itaconic acid (the mass concentration of itaconic acid in the solution is 1.5%) for 6min, and then taken out and irradiated in an electron accelerator (voltage 80keV, dose 50kGy), thereby obtaining a PTFE prepreg with high peel strength;

[0070] (4) two layers of PTFE prepreg obtained in step (3) are laminated, the size of the PTFE prepreg is selected as 380*280mm, 18μm-thick copper foils are covered on both sides of the laminated prepreg, and high-temperature lamination sintering treatment is performed, the specific conditions of the high-temperature lamination sintering treatment being: hot-pressing pressure 80kgf, hot-pressing temperature 375℃, and holding and pressure-keeping time 2.5h;

[0071] (5) after step (4) is completed, the temperature is lowered to room temperature, and then pressure is released, thereby obtaining a PTFE-based copper-clad plate with high peel strength.

[0072] Comparative Example 1

[0073] A method for preparing a PTFE copper-clad plate with high peel strength comprises the following steps:

[0074] (1) 100g of fluororesin emulsion, 83g of inorganic filler, and 1g of thickening agent are mixed by high-speed stirring for 1.5h, thereby obtaining a fluororesin dispersion;

[0075] (2) The dispersion liquid described in step (1) is coated on a copper foil (a releasable substrate), and is baked in a 350°C oven for 25 minutes, after which it is separated from the copper foil to obtain a PTFE prepreg;

[0076] (3) Two layers of the PTFE prepreg obtained in step (2) are laminated, and the PTFE prepreg is selected to have a size of 380x280 mm. Copper foils with a thickness of 18 μm are covered on both sides of the laminated prepreg, and high-temperature lamination sintering treatment is performed. The specific conditions of the high-temperature lamination sintering treatment are as follows: the hot-pressing pressure is 80 kgf, the hot-pressing temperature is 375°C, and the holding and pressure-maintaining time is 2.5 h;

[0077] (4) After step (3) is completed, the temperature is lowered to room temperature, and then the pressure is released, thereby obtaining a PTFE-based copper-clad plate with high peel strength.

[0078] Comparative Example 2

[0079] A method for preparing a PTFE copper-clad plate with high peel strength includes the following steps:

[0080] (1) 100 g of a fluororesin emulsion, 83 g of an inorganic filler, and 1 g of a thickening agent are mixed by high-speed stirring for 1.5 h to obtain a fluororesin dispersion liquid;

[0081] (2) The dispersion liquid described in step (1) is coated on a copper foil (a releasable substrate), and is baked in a 350°C oven for 25 minutes, after which it is separated from the copper foil to obtain a PTFE prepreg;

[0082] (3) The PTFE prepreg obtained in step (2) is immersed in a sodium-naphthalene complex for 6 minutes, and then is taken out and irradiated in an electron accelerator (voltage: 80 keV, dose: 50 kGy) to obtain a PTFE prepreg with high peel strength;

[0083] (4) Two layers of the PTFE prepreg obtained in step (3) are laminated, and the PTFE prepreg is selected to have a size of 380x280 mm. Copper foils with a thickness of 18 μm are covered on both sides of the laminated prepreg, and high-temperature lamination sintering treatment is performed. The specific conditions of the high-temperature lamination sintering treatment are as follows: the hot-pressing pressure is 80 kgf, the hot-pressing temperature is 375°C, and the holding and pressure-maintaining time is 2.5 h;

[0084] (5) After step (4) is completed, the temperature is lowered to room temperature, and then the pressure is released, thereby obtaining a PTFE-based copper-clad plate with high peel strength.

[0085] Experimental Example 1

[0086] Reference Figure 1 The PTFE prepreg obtained in step (2) in the above-described Example 1 is subjected to infrared spectrum analysis, and only C-F (1149 cm-1 and 1221 cm -1 ) absorption peaks. Correspondingly, the PTFE prepreg obtained by step (2) in Example 2-4, Comparative Example 1 was also analyzed by infrared spectroscopy, and the same situation was also had, only C-F (1149 cm -1 and 1221 cm -1 ) absorption peaks.

[0087] Referring to Figure 2 , the PTFE prepreg obtained by step (3) in Example 1 was analyzed by infrared spectroscopy, compared with before modification, the C-F absorption peak intensity was reduced after modification, and new peak position appeared in the infrared spectrum after modification: C=O absorption peak appeared at 1710 cm -1 , O-H bending (in-plane) absorption peak appeared at 1414 cm -1 , the appearance of the above new peaks proved the success of grafting. The PTFE prepreg obtained by step (2) in Example 2-4 was also analyzed by infrared spectroscopy, and the same result was obtained, compared with before modification, the C-F absorption peak intensity was reduced after modification, and new peak position appeared in the infrared spectrum after modification: C=O absorption peak appeared at 1710 cm -1 , O-H bending (in-plane) absorption peak appeared at 1414 cm -1 , the appearance of the above new peaks proved the success of grafting.

[0088] Experimental Example 2

[0089] The copper-clad PTFE sheets prepared by the preparation methods of Examples 1-4 and Comparative Example 1 were respectively taken, and their peel strength, dielectric constant, dielectric loss and high temperature resistance were detected; among them, the dielectric constant and dielectric loss were tested by the method of 2.5.5.2 in the electrical test method of 2.5 part of 《IPC-TM-650》standard; the peel strength was tested by the method of 2.4.8 part in 《IPC-TM-650》standard; the high temperature resistance test was tested by the method of 2.4.24.1 in 《IPC-TM-650》standard. The specific test results are shown in the following table:

[0090]

[0091] From the data measured in the above table, it can be seen that after the modification treatment of the PTFE prepreg by itaconic acid in the application, the surface energy of the PTFE is improved, and the bonding force between the PTFE and the copper foil is significantly improved, and the peeling strength is up to 3.27 N / mm; at the same time, from the dielectric loss test data, it can be seen that the data of examples 1-4 and comparative example 1 are basically the same, and it can be seen that the preparation method of the application does not damage the dielectric properties of the PTFE copper-clad plate; under the radiation condition of a dose of 35 kGy, the peeling strength can be the highest; based on the data of example 4 and comparative example 2, it can be seen that the traditional method of modifying PTFE by sodium and naphthalene complexing agent will have insufficient dielectric properties and mechanical properties.

[0092] Other examples and comparative examples (examples 5-12, comparative examples 3-10)

[0093] In order to further explore the influence of each step or parameter and other characteristics in the preparation method of the application on the technical effect, the application further provides the following examples 5-12, comparative examples 3-10 and their related test data are discussed.

[0094] 1. Discussion on itaconic acid concentration and immersion time

[0095] Based on example 3, the difference lies in adjusting the concentration of itaconic acid (the concentration of itaconic acid is the mass concentration of itaconic acid in the itaconic acid solution) and the immersion time, to obtain examples 5-8 and comparative examples 3-6, and the peeling strength, dielectric constant, dielectric loss and high temperature resistance of the PTFE copper-clad plate prepared by the above examples and comparative examples based on the method of experimental example 2 are detected, see the following table:

[0096] Example 5 Example 6 Example 7 Example 8 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Itaconic acid concentration 1.5％ 1.5％ 1％ 2％ 1.5％ 1.5％ 0.5％ 3％ Impregnation time 3 8 6 6 2 9 6 6 Peeling strength 1.87 2.78 2.11 2.34 1.45 2.67 1.67 2.19 Dielectric constant 2.221 2.230 2.224 2.216 2.225 2.235 2.227 2.267 Dielectric loss 0.0010 0.0012 0.0011 0.0014 0.0011 0.0013 0.0018 0.0016 High temperature resistance 60 60 60 60 60 60 50 50

[0097] The PTFE prepreg obtained by step (2) in each of the above examples 5-8 and comparative examples 3-6 is subjected to infrared spectrum analysis, compared with before modification, the C-F absorption peak intensity is reduced after modification, and a new peak appears in the infrared spectrum after modification: a C=O absorption peak appears at 1710 cm -1 , an O-H bending (in-plane) absorption peak appears at 1414 cm -1 , and the appearance of the above new peaks proves that the grafting of itaconic acid and PTFE in examples 5-8 and comparative examples 3-6 is successful.

[0098] Next, the influence of the mass concentration of itaconic acid in the itaconic acid solution and the impregnation time of the PTFE prepreg in the itaconic acid solution on the product performance is discussed in combination with the data of Example 3 and Examples 5-8 and Comparative Examples 3-6 in the above table. For the single variable of the impregnation time, the impregnation time of Comparative Example 3 is less than 3 min, which affects the peel strength (the peel strength is less than that of Examples 5 and 6, etc.), the impregnation time of Comparative Example 4 is greater than 8 min, which has no obvious influence on the peel strength, but the too long impregnation time affects the production efficiency; the impregnation time of 6 min can well balance the peel strength performance of the product and the production efficiency. For the single variable of the mass concentration of itaconic acid, the mass concentration of itaconic acid of Comparative Example 5 is the smallest, and the peel strength is also the lowest; the mass concentration of itaconic acid of Comparative Example 6 is higher than that of Examples 3 and 8, but the peel strength is lower than that of Examples 3 and 8, and the peel strength of Example 3 (corresponding to the itaconic acid concentration of 1.5%) is the highest.

[0099] 2. Discussion of irradiation conditions

[0100] Example 3 as the reference, the difference is that the irradiation conditions (irradiation voltage, irradiation dose) are adjusted to obtain Examples 9-12 and Comparative Examples 7-10, and the peel strength, dielectric constant, dielectric loss and high temperature resistance of the prepared PTFE copper-clad plate are detected based on the above method of Experimental Example 2, see the following table for details:

[0101]

[0102] The PTFE prepreg obtained by step (2) in each of the above Examples 9-12 and Comparative Examples 7-10 is subjected to infrared spectrum analysis, compared with before modification, the C-F absorption peak intensity is reduced after modification, and new peak positions appear in the infrared spectrum after modification: the C=O absorption peak appears at 1710 cm -1 , the O-H bending (in-plane) absorption peak appears at 1414 cm -1 , and the appearance of the above new peaks proves that the itaconic acid is successfully grafted with PTFE in the schemes of Examples 9-12 and Comparative Examples 7-10.

[0103] Next, the effect of irradiation voltage and irradiation dose on product performance is discussed in combination with the data of Example 3 and Examples 9-12 and Comparative Examples 7-10 in the above table. For the single variable of irradiation voltage, the peel strength of Comparative Example 7 is less than that of Examples 3, 9, and 10, because the irradiation voltage of Comparative Example 7 is less than 10 keV. The peel strength of Comparative Example 8 is less than that of Examples 3 and 10, because the irradiation voltage of Comparative Example 8 is greater than 100 keV. The peel strength of Example 3 is the highest, because the irradiation voltage of Example 3 is 80 keV. For the single variable of irradiation dose, the peel strength of Comparative Example 9 is less than that of Examples 3, 11, and 12, because the irradiation dose of Comparative Example 9 is less than 10 kGy. The peel strength of Comparative Example 10 is less than that of Examples 3, 11, and 12, because the irradiation dose of Comparative Example 10 is greater than 100 kGy. The peel strength of Example 3 is the highest, because the irradiation dose of Example 3 is 35 kGy.

[0104] Finally, it should be noted that the above-described embodiments are only preferred embodiments of the present application, and cannot be used to limit the scope of protection of the present application. Any non-essential changes and substitutions made by those skilled in the art based on the present application are within the scope of the present application.

Claims

1. A process for the production of a high peel strength PTFE copper clad plate, characterized by The method comprises the steps of grafting itaconic acid onto the surface of the PTFE prepreg, covering copper foils on both sides of the PTFE prepreg, and then performing high-temperature laminating sintering treatment.

2. The production method according to claim 1, characterized by, The PTFE prepreg is prepared by the following steps: applying a fluororesin dispersion liquid on a releasable substrate, then performing drying treatment, obtaining a fluororesin layer on the release paper, and separating the fluororesin layer from the substrate to obtain the PTFE prepreg.

3. The production method according to claim 2, characterized by, The fluororesin dispersion liquid comprises the following components: a fluororesin emulsion, an inorganic filler, and a thickening agent, wherein the weight fraction of the inorganic filler is 40%-70% of the total weight fraction of the fluororesin emulsion and the inorganic filler, and the weight fraction of the thickening agent is 0.5%-3% of the total weight fraction of the fluororesin emulsion and the inorganic filler.

4. The production method according to claim 3, characterized by, The fluororesin emulsion is a polytetrafluoroethylene resin emulsion, and the particle size of the fluororesin emulsion is 0.1-0.5 μm.

5. The preparation method according to claim 3, characterized in that, The viscosity of the fluororesin emulsion is 90-950 mPa·s.

6. The method of claim 1, wherein, The step of grafting itaconic acid onto the surface of the PTFE prepreg specifically comprises immersing the PTFE prepreg in an itaconic acid solution and then grafting itaconic acid onto the surface of the PTFE prepreg by radiation treatment.

7. The production method according to claim 6, characterized by, The immersion time of PTFE in the itaconic acid solution is 3-8 min, and the radiation treatment adopts electron beam radiation treatment, and the specific electron beam radiation conditions are: an irradiation voltage of 10 keV-100 keV and an irradiation dose of 5-100 kGy. Preferably, the irradiation voltage is 80 keV. Preferably, the irradiation dose is 35 kGy.

8. The method of any one of claims 6-7, wherein, The mass concentration of itaconic acid in the itaconic acid solution is 1%-2%. And / or, the solvent of the itaconic acid solution is a mixture of water and ethanol in a mass ratio of 2:

1.

9. The method of claim 1, wherein, Before covering the copper foils on both sides, a plurality of PTFE prepregs are laminated together, and then the high-temperature laminating sintering treatment is performed. Preferably, the specific conditions of the high-temperature laminating sintering treatment are: a hot pressing pressure of 50-100 kgf, a hot pressing vacuum degree of -80 kPa to -99 kPa, a hot pressing temperature of 350-400 ℃, and a holding and pressure maintaining time of 1-6 h.

10. A high-peel-strength PTFE copper-clad plate prepared by the method of any one of claims 1-9, wherein the peel strength of the PTFE copper-clad plate is 1.56-3.27 N / mm, and the dielectric constant is 2.192-2.432.

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